tissue analysis is an excellent way to determine if a crop is
actually getting the nutrients which are needed. This can help in
evaluating the fertilizer program up to the point of sampling and
allows adjustments to be made. However, it is a tool which must be
used with caution.
The tissue sampling
method is critical for success. The procedure is unique to each
crop. The plant must be at a specific stage of growth, and a
specific tissue must be selected. Failure to follow the prescribed
method for that crop will produce misleading results. Samples are
then quickly rinsed in distilled water an immediately sent to the
the analysis is done, the nutrient contents are compared with known
minimum values for that crop (critical values) and nutrient
deficiencies or excesses are identified.
more recent approach is to look at both the nutrient levels as well
as the ratios of the nutrients, a process known as Diagnostic
and Recommendation Integrated System (D.R.I.S.). This system shows a
lot of promise, but is still being fine tuned.
are certain things that plant analysis cannot do. It cannot predict
nutrient needs before planting. In the case of short term crops,
plant analysis does not identify problems early enough to solve
them. It also does not identify acidity problems or other soil
conditions which may affect uptake of the nutrients by the crop. It
is therefore not a substitute for soil analysis.
plant analysis is used as the sole method of determining nutrient
needs, it can give misleading information even when sampling is done
properly. A low level of nutrients in the tissue indicates that
something is wrong, but does not necessarily indicate that
fertilizers are needed. Nutrient uptake may have been inhibited by
problems such as root pests and diseases, waterlogging, drought etc.
adequate level of a nutrient in the tissue does not always indicate
that fertilizer application is unnecessary. Often, when one nutrient
deficiency is solved and the plants begin to grow, the levels of
other nutrients may fall below the adequacy level due to a process
known as dilution.
analysis is a powerful tool, but the results must be interpreted